You'll find it under the cowl on top of the frame rail on the drivers side. There should be a star in front of and behind the number.
If it is stock it is on the engine. Otherwise it is on the frame, drivers side about 4-6 inches back from the front of the cowl. You will have to lift the body off to see it. Also, you could use some 0000 steel wool to try to polish the "Stamp" out. Chris Nelson Kansas
That's only if, it is the original engine, will you find it to be the exact vin number of the car and will match the frame rail as mentioned.
I've heard that not all A's had vins stamped in the frame, so you might be looking for something that isn't there. Plus the vin is only going to be about 6 or 7 digits, I forget exactly.